CHAFF CLOUD RCS

CALCULATION

Anil PandeyAnil Pandey

WHAT IS CHAFF CLOUD?.

CHAFF CLOUD RCS CALCULATION

.

Import or Model

Geometry

Apply external

excitation

Define Far zone

sensor

Define FDTD

MeshRun SimulationPlot RCS Data

Run Chaff

Cloud Script

CHAFF CLOUD MODELING

• A chaff cloud forms the EM equivalent of a visual

smoke screen that can temporarily hide the target

from radar.

• Chaff consist of very thin dipoles cut to resonant

length ( normally lambda/2)

• Dispensed in the atmosphere to form a cloud of

scatterers, fired from ships or aircraft.

• Chaff can be used in different missions, but overall

the purpose of chaff is to mask the radar target

4

Chaff cloud generated in

using python script

PYTHON SCRIPT FOR CHAFF CLOUD GENERATION

.5

def setupGeometry():

pec = empro.activeProject.materials()["PEC"]

for i in range(NUMBER_OF_STRIPS):

# Modeling the strips

x = random.randrange(-STRIP_SPACING*SIZE_X, STRIP_SPACING*SIZE_X,1)

y = random.randrange(-STRIP_SPACING*SIZE_Y, STRIP_SPACING*SIZE_Y,1)

z = random.randrange(-STRIP_SPACING*SIZE_Z, STRIP_SPACING*SIZE_Z,1)

ang = random.randrange(0, 360,1)

p1 =V(x , y, z)* SCALED_UNIT

p2 = V(x+WIDTHS*math.sin(math.radians(ang)),(y-WIDTHS*math.cos(math.radians(ang))),z)

*SCALED_UNIT

p3 = V(x+WIDTHS*math.sin(math.radians(ang))+LENGTHS*math.cos(math.radians(ang)),(y-

WIDTHS*math.cos(math.radians(ang))+LENGTHS*math.sin(math.radians(ang))),z) *SCALED_UNIT

p4 = V(x+LENGTHS*math.cos(math.radians(ang)),y+LENGTHS*math.sin(math.radians(ang)),z)

*SCALED_UNIT

Stub = empro.toolkit.geometry.QuadPlate(p1,p2,p3,p4)

Stub.name = "Strip_X %d" % (i+1)

Stub.material = empro.activeProject.materials()["PEC"]

empro.activeProject.geometry().append(Stub)

# Defining Chaff Cloud Parameters

NUMBER_OF_STRIPS = 100

STRIP_SPACING = 4000

WIDTHS = 5

LENGTHS = 300

SIZE_X=1.5

SIZE_Y=2

SIZE_Z=1

#-------------------------------------------------

• Number of Strips

• Size of resonating strip ( length and width of

Strip)

• Size of Cloud

• Distribution type ( uniform, triangular, range….)

RCS : CHAFF CLOUD IN FRONT OF SPHERE

Incident Plane

wave Metallic

Strip Cloud

Metal Sphere

Conformal mesh to model tiny

metallic strips

RCS OF CHAFF COULD7

Blue – RCS of metal spear without

chaff cloud

Green- RCS of metal spear in

Presence of chaff cloud

LOCKHEED SR-71 BLACKBIRD

8

The structure is big (about 40 meter)SR-71

40 meter

Top View

Front View

Side View

CHAFF CLOUD ALONG WITH SR71 PLANE

.9

SR71 Plane

Chaff Cloud Generation Script

Chaff Cloud

CHAFF CLOUD PARAMETERS

.10

• Cloud Diameter = 18 meter

• More than 9000 metallic Strips

• Resonating Frequency = 0.5 GHz

• Length of Strip (lambda/2) = 300 mm

• Width of strip = 5 mm

9 meter

λ/2

2D RCS COMPARISON ( WITH AND WITHOUT CHAFF CLOUD).11

Phi=0 Degree cut

Freq-0.5 GHz

Theta=90 Degree cut

Freq-0.5 GHz

3D RCS COMPARISON ( WITH AND WITHOUT CHAFF CLOUD)

.12

RCS : Only Blackbird Plane RCS : Blackbird Plane with Chaff Cloud